After early tests of the Gerfaut la, Nord designed and built the Nord 1500-01 Griffon I research aircraft, which was intended to flight-test a combined turbojet-ramjet power unit. A delta wing aircraft with 60° of sweepback on the leading edge, the N 1500 had rwings with elevons for control in pitch and roll. Thus the tail unit comprised only swept vertical surfaces, and fixed foreplanes were mounted on each side of the forward fuselage. The Griffon I was flown for the first time on 20 September 1955. Initially powered by a 4100kg thrust SNECMA Atar 101G21 turbojet, it was flown later with a 3800kg thrust Atar 101F. At the completion of initial testing the airframe was modified to accept a 3500kg thrust Atar 101E3 turbojet within the ducting of an integral ramjet of Nord design, the turbojet being located just forward of the ramjet burners. Then redesignated N 1500-02 Griffon II, it was flown first on 23 January 1957, completing more than 200 test flights before the Nord research programme ended in 1959.